A vehicle's suspension system plays a vital role in serving to isolate the occupants of a vehicle from irregularities of the road surface and to provide a safe and comfortable mode of transportation. Because vehicles are designed to drive on a variety of road surfaces, occasionally a vehicle may encounter an exceptional (abnormal) road condition, such as debris, potholes, bumps and the like, which results in isolated large-scale suspension vibrations that may be felt by vehicle occupants. Adaptive or active suspension systems enable selective adjustment of the suspension characteristics such as damping and stiffness, responsive to the contact between the vehicle wheels and the abnormal road feature. In isolated incidents, this helps to improve the vehicle's ride comfort and handling.
Over time, however, the vehicle's suspension system may become degraded such that large-scale suspension vibrations are continuously induced and, in some instances, not felt by vehicle occupants. For example, a wheel suspension of the vehicle's suspension system can include at least a spring element that reduces stresses on the vehicle and hydraulic shock absorbers. The hydraulic shock absorbers are configured such that oscillations of at least the portion of the vehicle that is spring suspended is damped. Degradation (e.g., an impaired ability to damp the oscillations) of the hydraulic shock absorbers adversely affects the vehicle's ride comfort and handling. In other instances, recurring large-scale suspension vibrations may also be induced when, for example, the vehicle is driven for an extended period of time on a rough road surface. These recurring large-scale suspension vibrations also may affect vehicle control.
Due to the improved design of hydraulic shock absorbers, mounts, bushings, and isolation materials inside the vehicle that help to “block” the large-scale suspension vibrations from being transferred to vehicle occupants, early warning signs of suspension degradation and/or a rough road condition are difficult to detect. Further, while isolated large-scale vibrations that result from an encountered abnormal road condition may be felt by vehicle occupants, after passing the isolated event there is often no clear indication of related residual effects unless the vehicle is damaged. Thus, it is desirable to implement a vehicle on-board system that can detect continuous and/or recurring large-scale suspension vibrations and alert the vehicle driver to check the vehicle's suspension system for degradation and/or an undesired operational condition caused by the recurring large-scale suspension vibrations.